1Grade 9 Geography Mapping Skills – Map Scale Maps are very useful tools for locating things, determining direction or calculating distances.What? How do you calculate a real or actual distance from a paper map?
2Grade 9 Geography Mapping Skills – Map Scale Calculating real distances…You need two things from your map AND a mathematical formula to determine real distances:Map Distance – The measured distance on the mapScale – A ratio (i.e., each centimetre on the map is how far in real lifeFormula – MD/GD = scale where GD is Ground Distance (the real or actual distance)
3Grade 9 Geography Mapping Skills – Map Scale Map Distance (MD)With a ruler, you need to measure the distance ON THE MAP from your starting point to your finishing point.The example shows a trip starting in Istanbul and finishing near the border with Iran. With a ruler, measure the line. This is the distance on the map or Map Distance (MD)
4Grade 9 Geography Mapping Skills – Map Scale Scale is located on the map…usually along a bottom edgeScale is a statement of the relationship between distances on a map (i.e., Map Distance (MD)) and distances in real life (i.e., Ground Distance (GD)).As you know, a drawing made according to the scale will be an exact copy of the real object…only smaller.Scale is always presented as a ratio on a map. For example, scale is given as 1:25,000,000 which means 1 cm on a map is 25,000,000 cm in real life (or 250 km)
5Grade 9 Geography Mapping Skills – Map Scale FormulaThe formula for calculating the real distance (i.e., Ground Distance (GD)) is a ratio.If you know Map Distance (MD) and scale, you can “somehow” combine them to calculate GD.MD / GD = scale
6Grade 9 Geography Mapping Skills – Map Scale MD / GD = scaleExampleScale is 1:37,000,000 or 1 cm = 370 km or 1 / 370MD = 10.2 cmWhat is Ground Distance (GD)?MD / GD = 1 / 370Let GD = x10.2 / x = 1 / 370x = (10.2)(370) = 3,374The Ground Distance is 3,374 km
7Grade 9 Geography Mapping Skills – Map Scale MD / GD = scaleTry oneScale is 1:25,000,000 or 1 cm = 250 km or 1 / 250MD = 13.2 cmWhat is Ground Distance (GD)?MD / GD = 1 / 250Let GD = xThe Ground Distance is 3,300 km …right?